This invention relates to processes for coloring keratin fibers in which at least one pyridoxine, pyridoxal or pyridoxamine derivative is used, to colorants containing such compounds and to kits for use in the process according to the invention.
Keratin fibers in the context of the invention are understood to include pelts, wool, feathers and, in particular, human hair. Nowadays, human hair is treated in many different ways with hair-care preparations. Such treatments include, for example, the cleaning of hair with shampoos, the care and regeneration of hair with rinses and conditioners and the bleaching, coloring and shaping of hair with coloring and tinting formulations, wave formulations and styling preparations. Among these, formulations for modifying or shading the color of the hair play a prominent role.
Colorants or tints containing substantive dyes as their coloring component are normally used for temporary colors. Substantive dyes are based on dye molecules which are directly absorbed onto the hair and do not require an oxidative process for developing the color. Dyes such as these include, for example, henna which has been used since ancient times for coloring the body and hair. Corresponding colors are generally sensitive to shampooing so that an often unwanted change of shade or even a visible “decoloration” can occur.
By virtue of their intensive colors and good fastness properties which are achieved at relatively low coloring temperatures and in short coloring times, so-called oxidation colorants play a particular role in the coloring of keratin fibers, especially hair. Oxidation colorants contain a primary intermediate in a suitable, generally water-containing carrier. This primary intermediate forms the dye by oxidative coupling under the influence of atmospheric oxygen or oxidizing agents. The dye can be intensified and modified in shade by coupling with another primary intermediate or with so-called secondary intermediates which are not themselves able to form dyes.
Good oxidation dye precursors are expected to satisfy above all the following requirements: they must form the required color tones with sufficient intensity and fastness during the oxidative coupling reaction. In addition, they must be readily absorbed onto the fibers with no significant differences—particularly in the case of human hair—between damaged and freshly regrown hair (levelling behavior). They are expected to be fast to light, heat and the effect of chemical reducing agents, for example permanent wave lotions. Finally, if they are used to color hair, they should not overly stain the scalp and, above all, should be toxicologically and dermatologically safe. In addition, the color obtained, for example by blonding, should be easily removable from the hair if it does not meet the individual wishes of the user and is to be taken out.
Users of hair colorants seek inter alia to achieve a natural-looking hair color as the outcome of the coloring process. This is the case above all when gray hair is to be inconspicuously hidden by a natural-looking color. When it comes to obtaining natural-looking shades, considerable significance attaches to hair coloring and tinting formulations which color in shades of the red and brown range. Oxidation colorants in the red and brown range which are available, for example, in the combination of 2,4,5,6-tetraaminopyrimidine with 2-methyl resorcinol are not yet optimal in regard to the uniformity with which the color is absorbed. Golden tones have not yet been satisfactorily obtainable using conventional combinations of primary and secondary intermediates. In order to obtain a broad range of tones, substantive dyes inter alia may be used for shading. Substantive dyes are generally not fast to washing and, because of this, are not so suitable for combination with oxidation dyes.
A natural-looking hair color also comes from a coloring process where indole or indoline derivatives are used as precursors of so-called “nature-analogous” dyes in the hair colorant applied. According to WO 9906016 A1, partly or completely gray hair can be colored back to its original natural shade by using a combination of derivatives of indole or indoline with typical secondary intermediates, so that no significant difference from any naturally pigmented hair still present is visible. Blond to mid-brown colors are obtained. The dye combinations disclosed in WO 9906016 A1 give dark to black colors with no red which were always difficult to obtain with the traditional primary/secondary intermediate combinations.
The coloring of keratin fibers using “nature-analogous” dyes is setting a trend of achieving natural-looking colors even with natural or “nature-identical” dye precursors. Accordingly, it is desirable to be able to vary the color of the hair by adding an equally natural or “nature-identical” oxidation dye precursor of the secondary intermediate type. Access to a broader range of colors should thus be gained and an intensive color fast to washing and light obtained.
Besides optimizing the coloring effect of hair colorants, improving their compatibility is another problem to be addressed. Oxidative components, for example in hair colorants, have a damaging effect on the structure of hair keratin. The hair undergoes a weight loss and a measurable reduction in the denaturing temperature of the keratin. Increasing fragility, reduced combability of the hair and a deterioration in the body and hold of the hair are the outcome. In addition, structurally damaged hair has a dull, lackluster appearance. These problems should be counteracted with structure-improving additives in the coloring process, advantageously as constituents of the colorant itself.
For these reasons, there is a need for new oxidation dye precursors and active care ingredients which would enable the parameters mentioned to be improved, It has surprisingly been found that pyridoxine, pyridoxal or pyridoxamine derivatives excellently satisfy the requirements stated above.
Pyridoxine and other compounds of the vitamin B6 group have been mentioned as components in hair tonics for reducing refatting and for stimulating hair growth. EP 0678293 A2 proposes topical compositions containing pyridoxine tripropionate for treating the hair and skin. EP 001079 A1 describes anti-seborrheic cosmetic compositions containing pyridoxine tripalmitate as their active ingredient.
EP 873744 A2 describes carbonyl compounds, inter alia pyridoxal, in combination with amines, hydroxy compounds, peptides, CH-active compounds and other components as dye precursors in preferably non-oxidative hair colorants.
Hair colorants containing derivatives of pyridoxine, pyridoxal or pyridoxamine as effective oxidation dye precursors and as structure-improving additives are unknown to the expert.
It has surprisingly been found in comparative coloring tests that vitamin B6 and certain derivatives have secondary intermediate properties. In particular, it was found that the use of such compounds as secondary intermediate component in hair colorants adds medium golden blond colors to the range of colors. It was also found that the use of the compounds according to the invention during the coloring process leads to an improvement in the structure of hair keratin.